Journal article
Systematic variations of Ion hydration in aqueous alkali metal fluoride solutions
The Journal of Physical Chemistry B, Vol.123(50), pp.10868-10876
2019
Abstract
Aqueous solutions of three alkali metal fluorides—NaF, KF, and CsF—have been studied by dielectric relaxation spectroscopy (DRS) over the frequency range 0.2 ≲ ν/GHz ≤ 89 at 25 °C and at concentrations 0.05 ≲ c/mol L–1 ≲ 1. The combination of these measurements with analogous literature data for RbF(aq) and M′Cl(aq) (M′ = Li, Na, K, and Cs) made possible a systematic analysis of the hydration of F– and the alkali metal cations. Unlike the other halide ions, F– was found to have a well-defined hydration shell which contains ∼7 water molecules, consistent with the appearance of a “slow”-water mode at ∼10 GHz in the spectra. Limiting total effective hydration numbers (Zt0) for M′F(aq), obtained from the solvent-related modes, did not follow a simple sequence, varying in the order CsF < NaF < RbF < KF. However, it is shown that this anomalous sequence results from subtle variations in the strength of the M′+–OH2 bonding. Thus, it was established that Zib0(M′+) values, corresponding to the numbers of strongly (“irrotationally”) bound (ib) water molecules around the cations, do vary with charge density in the order Li+ ≫ Na+ > K+ > Rb+ > Cs+. It was also found that Zs0(M′+), the number of moderately bound (“slow”) water molecules, varied in the same order: K+ > Rb+ > Cs+. However, the presence of ib water molecules in the hydration shells of Li+ and Na+ attenuates their further interaction with surrounding water molecules such that Zs0(M′+) ≈ 0 for both ions.
Details
- Title
- Systematic variations of Ion hydration in aqueous alkali metal fluoride solutions
- Authors/Creators
- R. Buchner (Author/Creator)W. Wachter (Author/Creator)G. Hefter (Author/Creator)
- Publication Details
- The Journal of Physical Chemistry B, Vol.123(50), pp.10868-10876
- Publisher
- American Chemical Society
- Identifiers
- 991005543781307891
- Copyright
- © 2019 American Chemical Society
- Murdoch Affiliation
- Chemistry and Physics
- Language
- English
- Resource Type
- Journal article
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- 2 Chemistry
- 2.89 Ionic, Molecular & Complex Liquids
- 2.89.677 Liquid Water
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- Chemistry, Physical
- ESI research areas
- Chemistry